Multi-ply, metal-clad sandwich panels

ABSTRACT

A multi-ply metal-plated sandwich panel made up of: 1. A FIRST (OUTER) PLY OF A CORROSION-RESISTANT METAL HAVING A THICKNESS OF FROM 0.05 TO 1 MM; 2. A SECOND (INNER) PLY OF AN ETHYLENE COPOLYMER CONTAINING CARBOXYL GROUPS HAVING A THICKNESS OF 0.01 TO 0.4 MM AS A HOTMELT ADHESIVE; 3. A THIRD (INNER) PLY OF A SPECIAL ADHESION PROMOTER HAVING A THICKNESS OF 0.01 TO 0.4 MM; 4. A FOURTH (INNER) PLY OF A THERMOPLASTIC HAVING A THICKNESS OF 2 TO 20 MM; 5. A FIFTH (INNER) PLY OF A SPECIAL ADHESION PROMOTER HAVING A THICKNESS OF 0.01 TO 0.4 MM; 6. A SIXTH (INNER) PLY OF AN ETHYLENE COPOLYMER CONTAINING CARBOXYL GROUPS HAVING A THICKNESS OF 0.01 TO 0.4 MM AS A HOTMELT ADHESIVE; AND 7. A SEVENTH (OUTER) PLY OF A CORROSION-RESISTANT METAL HAVING A THICKNESS OF 0.05 TO 1 MM.

a United States atent 1191 1111 3,767,521

Glaser et a1. Oct. 23, 1973 [54] MULTl-PLY, METAL-CLAD SANDWICH3,459,700 8/1969 Richards 161/217 X PANELS 3,623,943 6/1970 AltenpohL.161/216 X 1 3,689,334 9/1972 Dermody 161/254 X 1 Inventors: RudolfGlaser, Ludwigshafen; 3,711,365 1/1973 Pyle 161/252 x Alfred Hofmann,3,712,848 1/1973 Casey et a1. 161/216 X Bobenheim-Roxheim; Klaus3,712,849 1/1973 Robbiati 161/218 Bronstert, Carlsberg, all of GermanyPrimary Examiner--Harold Ansher 3 B l & k [7 1 Asslgnee adische Am mSoda Att0rneyJohnston, Root, OKeeffe, Keil, Thompson Aktiengesellschaft,& Sh t1 ff Ludwigshafen/Rhein, Germany ur e 1 1 pp 187,336 A multi-plymetal-plated sandwich panel made up of: 1. a first (outer) ply of acorrosion-resistant metal [30] Foreign Application Priority Data 2 havmgd zF j f g ih l 1 mm; 1

. a secon mner py 0 an e yene copo ymer 061. 7, 1970 Germany r 20 49226.6 containing carboxyl groups having a thickness of 0.01 to 0.4 mm asa hot-melt adhesive; [52] US. Cl 161/216, 11661521575 1l6611//22l584, 3a third (inner) p y of a Special adhesion promoter 51 1111. C1 B32b15/08, B32b 27/32 havmg a thickness of 58 M is h 4. a fourth (mner) plyof a thermoplast1c having a 1e 0 care thickness ofz to 20 mm;

5. a fifth (inner) ply of a special adhesion promoter Reerences Citedhaving a th1ckness of 0.01 to 0.4 mm;

6. a sixth (mner) ply of an ethylene copolymer UNITED STATES PATENTScontaining carboxyl groups having a thickness of 2,580,050 12/1951Sparks et al. 161/216 X 0.01 to 0.4 mm as a hot-melt adhesive; and2,916,469 12/1959 Lai. 161/216 X 7 a v nth (outer) ply of acorrosion-resistant 3,127,296 3/1964 Guzlak 161/216 X metal having athickness of 005 to 1 3,439,064 4/1969 Makowski et al..... 161/217 X3,447,460 6/1969 Vincent et 211..., 161/216 X 6 Claims, 1 Drawing FigureMULTl-PLY, METAL-(SLAB SANDWICH PANELS The present invention relates tomulti-ply metal-clad sandwich panels made up of:

11. a first (outer) ply of a corrosion-resistant metal having athickness of 0.05 to 1 mm;

2. a second (inner) ply of a hot-melt adhesive having a thickness of0.01 to 0.4 mm;

3. a third (inner) ply of an adhesion promoter having a thickness of0.01 to 0.4 mm;

4. a fourth (inner) ply of a thermoplastic having a thickness of 2 to 20mm;

5. a fifth (inner) ply of an adhesion promotor having a thickness of0.01 to 0.4 mm;

6. a sixth (inner) ply of a hot-melt adhesive having a thickness of 0.01to 0.4 mm; and

7. a seventh (outer) ply of a corrosion-resistant metal having athickness of 0.05 to 1 mm.

The individual plies are shown in the accompanying drawing.

Panels of this type have a number of advantages over comparablestructures but have certain disadvantages. For example it is adisadvantage that the adherence of the individual plies of the unit toone another is so low that they become detached from one another uponfairly slight mechanical stress. It is another disadvantage that theunits have inadequate stiffness for some applications.

The present invention has as an object the provision of panels of thetype defined above which have the said disadvantage to a far lesserextent or not at all.

This object is achieved by units in which:

(1) the second and sixth inner plies (2) and (6) consist of a specialquaternary polymer; and

(II) the third and fifth inner plies (3) and (5) consist of a ternarymixture of special polymers. According to the present inventiontherefore multiply metal-clad sandwich panels consist of 1. a first(outer) ply of a corrosion-resistant metal having a thickness of from0.05 to 1 mm;

2. a second (inner) ply of a hot-melt adhesive having a thickness offrom 0.01 to 0.4 mm;

3. a third (inner) ply of an adhesion promoter having a thickness offrom 0.01 to 0.4 mm;

4. a fourth (inner) ply of a thermoplastic having a thickness of from 2to 20 mm; I

5. a fifth (inner) ply of an adhesion promoter having a thickness offrom 0.01 to 0.4 mm;

6. a sixth (inner) layer of a hot-melt adhesive having a thickness offrom 0.01 to 0.4 mm; and

7. a seventh (outer) ply of a corrosion-resistant metal 7 having athickness of 0.05 to 1 mm. The panels of the invention are characterizedas follows:

. their second and sixth (inner) plies (2) and (6) consist of aquaternary polymer which contains polymerized units of 60 to 90 parts byweight of ethylene, 0.5 to 20 parts by weight of an ethylenicallyunsaturated carboxylic acid, 0.5 to 20 parts by weight of an ester of anethylenically unsaturated carboxylic acid and 0.3 to 5 parts by weightof isobutylene, the sum of the parts being 100; and

11. their third and fifth (inner) plies (3) and (5) consist of a ternarymixture of:

a. a homopolymer of a styrene or a copolymer of a styrene which containspolymerized units of up to 35 percent by weight of at least one othermonomer;

b. a homopolymer of a C to C monoolefin or a copolymer of a C, to Cmonoolefin which contains up to 35 percent by weight of polymerizedunits of at least one other monomer; and

c. a block copolymer having the formula A-B in which A is a block of apolystyrene having a molecular weight of from 10,000 to 150,000, and Bis a block of a polyolefin having a molecular weight of from 10,000 to200,000 in which not more than 10 percent of the carbon-carbon bonds areolefinically unsaturated, the molar ratio of AB being from 10:90 to :30,

with the proviso that the ratio by weight of components a and b lieswithin the range from 4:1 to 1:4, that the total content of component 0in the whole mixture is from 5 to 70 percent by weight, and the termstyrene refers to a compound having the general formula:

in which R denotes H or CH Ejengtes tl to C alkyl and n denotes zero,'16??? Concerning the plies of the panels of the invention the followingdetails may be given I The layers 1 and 7 may for example consist ofcopper, aluminum, brass or stainless steel.

The plies 2 and 6 consist of a quaternary polymer having the compositiondescribed above. These polymers are known from polymer chemistry. Theyare obtained in the high pressure polymerization of ethylene for examplewhen polymerization is carried out in the presence of esters ofethylenically unsaturated carboxylic acids derived from tertiary and/orprimary and/or secondary alcohols, at temperatures at'which the tertiary or secondary ester groups are wholly or partly eliminated from thepolymer. The polymers should advantageously have the followingcharacteristics: density from 0.9 to 1.1 g/ccm, crystalline fractionless than 60 percent, Shore hardness C from 50 to 90. It has been foundthat quaternary polymers which are particularly suitable for the purposeof the present invention are those which contain polymerized units of 71to parts by weight of ethylene, 3 to 9 parts by weight of an aliphaticethylenically unsaturated C to C carboxylic acid, 1 to 20 parts byweight of a C to C alkyl ester of an aliphatic ethylenically unsaturatedC to C carboxylic acid and 0.3 to 5 parts by weight of isobutylene, thetotal of the parts by weight always being 100. The polymers of plies 2and 6 in the panels may be identical or different from each other.

The plies 3 and 5 consist of a ternary mixture of the compositiondescribed above. The individual components of the mixture are also knownfrom polymer chemistry. Homopolymers and particularly homopolymers ofsimple styrene (i.e. styrene not hearing any substituents) are preferredas component a. Examples of copolymers are copolymers of simple styrenewith a-methylstyrene, maleic anhydride, acrylic acid and/or butadiene.The polymers are preferably modified to make them impact-resistant.

Preferred components b are again homopolymers, especially homopolymersof ethylene having a density in the range from 0.918 to 0.930 g/ccm.Homopolymers of propylene are however also very suitable. Examples ofcopolymers are copolymers of C, to C monoolefins with one another andalso copolymers of these monoolefins, particularly of ethylene, withvinyl esters such as vinyl acetate and vinyl propionate.

Particularly suitable components c are block copolymers which have beenobtained by hydrogenation of corresponding block copolymers of ahomopolymer block of simple styrene and a 1,4-homopolymer block ofbutadiene.

Block copolymers having the formula A-B can be prepared by conventionalmethods, for example by first polymerizing a vinylaromatic monomer insolution in a hydrocarbon with an alkyl lithium catalyst and furtherpolymerizing on the living" ends of the chain in the second stage with a1,3-diene monomer.

It has been found that block copolymers in which the block of polystyrne(A) has a molecular weight of from 20,000 to 80,000 and the block ofpolyolefin (B) has a molecular weight of from 20,000 to 100,000, theratio of A:B preferably being from 30:70 to 60:40 are particularly wellsuited for the purposes of the present invention. In the case of theternary mixture itself it is advantageous for the weight ratio of thecomponents a and b to be within the range from about 1.5:l to 1:1 andfor the total content of component c in the mixture to be about 20percent by weight. The mixture can be prepared in a simple manner, forexample by mixing the components in the necessary ratio, for example ina kneader or extruder. In the panels the tertiary mixtures of plies 3and may be identical in composition or may be different from oneanother.

Ply 4 consists of a thermoplastic material. These include plastics basedon polyvinylaromatics, particularly unmodified polymers of styrene andthose whichhave been modified to make them impact-resistant, and alsocopolymers of styrene with other polymerizable monomers, for examplewith a-methylstyrene or maleic anhydride, and the copolymers may also begraft copolymers of styrene, for example with acrylic acid and/orbutadiene. Other suitable thermoplastics are polyethylenes, particularlythose having high density (0.945 to 0.960 g/ccm), polypropylenes andalso copolymers of ethylene and of propylene.

1n the production of panels according to the invention is is generallyadvantageous to use the hot-melt adhesive of plies 2 and 6 and theadhesion promoters of plies 3 and 5 in the form of single films of thesubstances concerned or in the form of double films (twoply films) ofthe appropriate substances of plies 2 and 3 and 6 and 5. Since theadhesive effect of the hot-melt adhesive and the adhesion promoter onlyoccurs when these are contacted in the plastic condition with oneanother and with the other plies of the panel, the hotmelt adhesive andadhesion promoter have to be used at an elevated temperature (90 to270C, particularly 150 to 240C).

The panels may be made by conventional methods. For example a suitablemethod consists in laying a metal foil (intended for ply l) in a platenpress, and laying thereon in turn a film of hot-melt adhesive (intendedfor ply 2), a film of an adhesion promoter (intended for ply 3), a ply4, a film of an adhesion promoter (intended for ply 5), a film ofhot-melt adhesive (intended for ply 6), and a metal foil (intended forply 7). The whole can then be pressed in a frame at an elevatedtemperature to give an intimate bond. The panels may also be obtainedcontinuously by an analogous method.

Because of their very high flexural rigidity the panels are suitable forexample for prefabricated house construction, shipbuilding, automobileconstruction and also as partitions in building construction.

The commercial quaternary polymer (hot-melt adhesive) used in the formof a film in the following example contains 86.3 parts by weight ofethylene, 3.8 parts by weight of acrylic acid, 8.2 parts by weight oft-butyl acrylate and 1.7 parts by weight of isobutylene in polymerizedform; it has a density of 0.928 g/ccm, its crystalline fraction is lessthan 50 percent and its Shore hardness C is 67.

The ternary mixture used in the example in the form of a film isobtained as follows A mixture is prepared in a kneader (kneading period:5 minutes, temperature of the material: C) from a. 48 percent by weightof a styrene homopolymer (modified with butadiene rubber to make itimpact-resistant, weight ratio of styrene homopolymer: butadiene rubber10:2);

b. 31 percent by weight of an ethylene homopolymer (density 0.918 g/ccm;MFl 190/2.l6 1.5 g/ten minutes) and c. 21 by weight of a hydrogenatedtwo block copolymer of styrene and 1,4-butadiene (formula AB in which Ais a polystyrene block having a molecular weight of 60,000 and B is apolyolefin block having a molecular weight of 70,000 in which 2.5percent of the carbon-carbon bonds are olefinically unsaturated; themolar ratio A:B is 1.5:l

The mixture is then processed into a film by a conventional method.

EXAMPLE The following are placed in sequence in a platen press: 1. a 0.5mm aluminum foil, 2. a 0.1 mm film of hot-melt adhesive, 3. a 0.08 mmfilm of adhesion promoter, 4. a 3 mm board of a styrene homopolymermodified to make it impact-resistant, 5. a 0.08 mm film of adhesionpromoter, 6. a 0.1 mm film of hot-melt adhesive and 7. a 0.5 mm aluminumfoil. The whole is then pressed to make an intimate assembly at 200 Cfor three minutes at a pressure of 0.5 kg/cm.

The panel thus obtained has very good flexural stiffness; its individualplies adhere very firmly to one another.

We claim: 1. A multi-ply, metal-clad sandwich panel made up of 1. afirst (outer) ply of a corrosion resistant metal having a thickness of0.05 to 1 mm;

2. a second (inner) ply of a hot-melt adhesive having a thickness of0.01 to 0.4 mm;

3. a third (inner) ply of an adhesion promoter having a thickness of0.01 to 0.4 mm;

4. a fourth (inner) ply of a thermoplastic having a thickness of 2 to 20mm;

5. a fifth (inner) ply of an adhesion promoter having a thickness of0.01 to 0.4 mm;

6. a sixth (inner) ply of a hot-melt adhesive having a thickness of 0.01to 0.4 mm; and

7. a seventh (outer) ply of a corrosion-resistant metal having athickness of 0.05 to 1 mm, wherein I. said second and sixth (inner)plies (2) and (6) consist of a quaternary polymer containing 60 to 90parts by weight of ethylene units, 0.5 to 20 parts by weight of anethylenically unsaturated carboxylic acid, 0.5 to 20 parts by weight ofan ester of an ethylenically unsaturated carboxylic acid and 0.3 to 5parts by weight of isobutylene, the total of the parts always being 100,and II. said third and fifth (inner) plies (3) and (5) consist of aternary mixture of: a. a homopolymer of a styrene or a compolymer of astyrene which contains up to 35 percent by weight of other monomer inpolymerized form; a homopolymer of a C to C monoolefin or a copolymer ofa C to C monoolefin which contains up to 35 percent by weight ofpolymerized units of other monomers; and c. a block copolymer having theformula AB in which A denotes a block of a polystyrene having amolecular weight of from 10,000 to 150,000; B denotes a block of apolyolefin having a molecular weight of from 10,000 to 200,000 in whichnot more than percent of the carbon-carbon bonds are olefinicallyunsaturated; and the molar ratio of A:B is from 10:90 to 70:30, with theproviso that the ratio by weight of the components a and b is within therange from 4:1 to 1:4, that the total content of component c in themixture is from 5 to 70 by weight and that the term styrene means acompound having the general formula:

in which R denotes H or CH R denotes C to C alkyl and n denotes zero, 1to 2.

2. A multi-ply, metal-clad sandwich panel as claimed in claim 1 whereinplies 1 and 7 consist of copper, aluminum, brass or stainless steel.

3. A sandwich panel as claimed in claim 1 wherein the polymer 'of plies2 and 6 has a density of from 0.9 to 1.1 g/ccm, a crystalline fractionof less than 60 percent, and a Shore hardness C of from 50 to 90.

4. A sandwich panel as claimed in any of claim 1 wherein the quaternarypolymer of plies 2 and 6 consists of 71 to parts by weight of ethyleneunits, 3 to 9 parts by weight of an aliphatic ethylenically unsaturatedC to C carboxylic acid, 1 to 20 parts by weight of a C to C alkyl esterof an aliphatic ethylenically unsaturated C to C carboxylic acid and 0.3to 5 parts by weight of isobutylene, the parts totalling 100.

5. A sandwhich panel is claimed in any of claim 1 wherein component 0 isa block copolymer in which the block of polystyrene has a molecularweight of 20,000 to 80,000 and the block of polyolefin B has a molecularweight of 20,000 to 100,000.

6. A sandwich panel as claimed in claim 5 wherein the ratio by weight ofA:B is from 30:70 to 60:40.

Patent 767,521 Dated October 2'2, 1972 Inventor(s) Rudolf Glaser et 8.1

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 1, line 12, "promoter" should read n promotera Column 3, line 18,"polystyrne" should read polyesyrene column 4, line 16, insert u after"follows".

Column 4, line 26, insert percent after "21".

Column 5, lihe l4, crzumpolymer" should read copolymer Column 5, line32, insert percent after "70".

Signed and sealed this 1st day of Oetober 1974.,

(SEAL) Attest: I

McCOY Ma GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents FORM po'wso YUSCOMM-DC coon-P09 US, GOVERNMENT PRINTING OFFICE:I969 0-365-334,

1. FIRST (OUTER) PLY OF A CORROSION-RESISTANT METAL HAVING A THICKNESSOF FROM 0.05 TO 1 MM;
 2. A SECOND (INNER) PLY OF AN ETHYLENE-COPOLYMERCONTAINING CARBOXYL GOUPS HAVING A THICKNESS OF 0.01 TO 0.4 MM AS AHOT-MELT ADHESIVE;
 2. a second (inner) ply of a hot-melt adhesive havinga thickness of 0.01 to 0.4 mm;
 2. A multi-ply, metal-clad sandwich panelas claimed in claim 1 wherein plies 1 and 7 consist of copper, aluminum,brass or stainless steel.
 3. A sandwich panel as claimed in claim 1wherein the polymer of plies 2 and 6 has a density of from 0.9 to 1.1g/ccm, a crystalline fraction of less than 60 percent, and a Shorehardness C of from 50 to
 90. 3. a third (inner) ply of an adhesionpromoter having a thickness of 0.01 to 0.4 mm;
 3. A THIRD (INNER) PLY OFSPECIAL ADHESION PROMOTER HAVING A THICKNESS OF 0.01 TO 0.4 MM;
 4. AFOURTH (INNER) PLY OF A THERMOPLASTIC HAVING A THICKNESS OF 2 TO 20 MM;4. a fourth (inner) ply of a thermoplastic having a thickness of 2 to 20mm;
 4. A sandwich panel as claimed in any of claim 1 wherein thequaternary polymer of plies 2 and 6 consists of 71 to 90 parts by weightof ethylene units, 3 to 9 parts by weight of an aliphatic ethylenicallyunsaturated C3 to C4 carboxylic acid, 1 to 20 parts by weight of a C1 toC8 alkyl ester of an aliphatic ethylenically unsaturated C3 to C4carboxylic acid and 0.3 to 5 parts by weight of isobutylene, the partstotalling
 100. 5. A sandwhich panel is claimed in any of claim 1 whereincomponent c is a block copolymer in which the block of polystyrene has amolecular weight of 20,000 to 80,000 and the block of polyolefin B has amolecular weight of 20,000 to 100,
 000. 5. a fifth (inner) ply of anadhesion promoter having a thickness of 0.01 to 0.4 mm;
 5. A FIFTH;(INNER) PLY OF A SPECIAL ADHESON PROMOTER; HAVING A THICKNESS OF 0.01 TO0.4 MM;
 6. A SIXTH (INNER) PLY OF AN ETHYLENE COPOLYMER CONTAININGCARBOXYL GROUPS HAVING A THICKNESS OF 0.01 TO 0.4 MM AS A HOT-MELTADHESIVE; AND
 6. a sixth (inner) ply of a hot-melt adhesive having athickness of 0.01 to 0.4 mm; and
 6. A sandwich panel as claimed in claim5 wherein the ratio by weight of A:B is from 30:70 to 60:40.
 7. ASEVENTH (OUTER) PLY OF A CORROSION-RESISTANT METAL HAVING A THICKNESS OF0.05 TO 1 MM.
 7. a seventh (outer) ply of a corrosion-resistant metalhaving a thickness of 0.05 to 1 mm, wherein I. said second and sixth(inner) plies (2) and (6) consist of a quaternary polymer containing 60to 90 parts by weight of ethylene units, 0.5 to 20 parts by weight of anethylenically unsaturated carboxylic acid, 0.5 to 20 parts by weight ofan ester of an ethylenically unsaturated carboxylic acid and 0.3 to 5parts by weight of isobutylene, the total of the parts always being 100,and II. said third and fifth (inner) plies (3) and (5) consist of aternary mixture of: a. a homopolymer of a styrene or a compolymer of astyrene which contains up to 35 perceNt by weight of other monomer inpolymerized form; b. a homopolymer of a C2 to C4 monoolefin or acopolymer of a C2 to C4 monoolefin which contains up to 35 percent byweight of polymerized units of other monomers; and c. a block copolymerhaving the formula A-B in which A denotes a block of a polystyrenehaving a molecular weight of from 10, 000 to 150,000; B denotes a blockof a polyolefin having a molecular weight of from 10,000 to 200,000 inwhich not more than 10 percent of the carbon-carbon bonds areolefinically unsaturated; and the molar ratio of A:B is from 10:90 to70: 30, with the proviso that the ratio by weight of the components aand b is within the range from 4:1 to 1:4, that the total content ofcomponent c in the mixture is from 5 to 70 by weight and that the term''''styrene'''' means a compound having the general formula: